A. Technical Field
The present invention relates generally to the field of electrical power measurement.
B. Background of the Invention
Electricity is generally measured in terms of an amount of total energy consumed over a given time. Electricity meters generally measure total power consumed by measuring the voltage and the current at a given instant in time and integrating the product of the measured voltage and current over desired time period.
Typically, a power measurement system comprises a line side device coupled to the AC power line to extract measurement signals, a host side device and a coupling device coupled between the line side device and the host side device. The coupling device is used to isolate the host side device from the relative high voltage AC power line for protection purpose.
U.S. Pat. No. 8,144,446 discloses the usage of a pulse transformer as barrier isolation to electrically isolate the host side device from the line side device. However, pulse transformer is expensive and susceptible to magnetic tamper. Pulse transformer with tamper resistance will further increase the cost. It is challenging to pass EMI test for pulse structure because of its low impedance nature and associated drive circuits.
Optical isolator, also called opto-isolator, may be used as a barrier isolator for power measurement system. Optical isolators are relatively expensive and affordable optical isolators typically have low operation speed (<10 kb/s) and thus limited system performance.
Therefore, it would be desirable to implement improved coupling method and interface with good combination of affordability and performance.